DetailsSmartwool Size Chart The Merino 250 baselayers are a favorite for good reason. They're warm, deliciously comfortable, and smartly breathable. So it may be time to give yourself over to the Smartwool version of the little black dress. Slim fitting and crew necked, the Merino 250 Solid Dress is made from 100% Merino. It feels peach-fuzz soft next to your skin, and it'll keep its great shape for many occasions.